Something more... a Woody?

[rankot]

I have replaced 100p ceramic cap which is parallel with diodes with 220p mylar and most of the noise is gone. Probably some of "acoustic" sparkle too, but not much. I have also found out that it is much better to use B10k potentiometers instead of A10k for top/bottom control.

And I used multiturn trim pot 500k for top gain control, but turning it doesn't seem to change things much.

[rankot]

I've tried to add 100p capacitors in parallel with all feedback resistors hoping it will reduce HF noise, but not much have changed. However, I like this pedal with my bass, it really gives it A PUNCH, so I can live with some noise, for now

[rankot]

I even tried this with a switch for different excited diodes. 1N34A's make a sound with less highs, while no diodes at all sound the same as default 1N4148's.

[Mark Hammer]

Try this: stick a back-to-back pair of Schottky diodes between the output of the fixed allpass stage and the input of the "Top" level pot, in series with the signal. , and reduce the value of the 12k resistor to maybe 6k8.

The Schottkys will "steal" some of the high end level, though not much.  Reducing the 12k resistor on the Top control output to maybe 6k8 will bring the high-end level back up to compensate.

The Schottky pair will serve as a VERY crude gate, blocking passage of anything below their forward voltage.  While we would not tolerate what they do if serving as a gate for an overall audio signal, since they would be blocking passage of what is an already distorted signal, it's not like they'd be doing anything "wrong" in this application.

I used this trick to gate out annoying whine in a ring modulator, and it worked nicely, if maybe not quite as well as a more sophisticated noise gate would have.  There's a pretty good chance it will work as well here.

[rankot]

I'll try this, but I still can't figure out why 1N4148 diodes sound the same as without them?

I'll check again in the morning, when I get some rest.

[Mark Hammer]

Many op-amps will distort when the gain is too high. I recall well many years back when forum members would remark that their Distortion+ build sounded the same whether they used a pair of clipping diodes to ground or not.  Some companies (e.g., Tech 21, and Black Cat) have made a point of using the "natural" clipping tendencies of op-amps aiming for too much gain.

Of course, whether the clipping you hear with and without the diodes is exactly the same, or simply distorting when you didn't expect it to, is another matter.

[rankot]

I have finally added a simple tone control with pot and capacitor right after volume pot. It makes adjustable low pass filter and does just what I wanted - a possibility to reduce hiss a little, while keeping overall effect.